1. Field of the Invention
The present invention pertains to a porous media impingement type air filter system including a filter unit which is operably connected to a mechanical vibrator and is supported on a flexible wall member forming a closure of one end of the filter chamber. The filter unit is adapted for use in conjunction with pneumatic bulk material conveying systems.
2. Background Art
In the art of porous media impingement or barrier type filter systems used for filtering dust and particulate matter out of a moving air stream, it has always been a problem to prevent unwanted clogging of the filter by accumulation of caked material on the filter media. The filter media must, inherently, accumulate particulate material in the performance of its function. However, continued accumulation of material eventually reduces the fluid flow area through the filter and increases the flowstream back pressure.
Several techniques have been developed to provide for the so called self-cleaning of impingement or barrier type air filter units. One approach involves providing apparatus for producing periodic pulsed jets or blasts of high velocity air in the reverse direction of the normal flow of air through the filter element to knock accumulated material off of the media. Such systems typically require a relatively high pressure source of compressed air to provide sufficient energy of the reverse flow to remove material accumulated on the filter media. This is particularly true for the preferred type of filter units which have a substantially rigid cylindrical element including a pleated media such as porous paper or similar material.
Another technique which has been developed for impingement or barrier type air filter units pertains to various arrangements for vibrating the filter element to periodically or continuously effect the removal of accumulated particulate material on the filter media. Known types of mechanical vibrating systems require specialized filter element structures such as, for example, the type of system wherein the filter element structure itself including the filter media is mechanically twisted or deflected to remove the accumulated material. This type of filter media cleaning system has the disadvantage of shortening the life of the filter due to mechanical fatigue of the filter media and adjacent supporting structure which is constantly being flexed or deflected.
Several other mechanical vibrating systems have been developed for various types of porous media impingement filters, all of which are relatively mechanically complex and are relatively unreliable due to the fact that the structure around and including the filter element is being constantly stressed in a cyclic manner resulting in early fatigue failure of one or more parts of the structure.
Accordingly, there has been a longfelt need for a self-cleaning type filter system which is adapted to utilize the preferred type of filter element characterized by a pleated porous media supported by associated structure which forms a substantially rigid and easily fabricated unit. Such types of filter elements have not easily lent themselves to use in connection with mechanical vibrating devices for continuously or periodically cleaning the filter media by vibrating or shaking the entire filter unit. However, the present invention provides an arrangement which mechanically vibrates the filter element with a particularly advantageous structure which is adapted for several filtering applications. In particular, one embodiment of the self-cleaning air filter system of the present invention is adapted for used in conjunction with pneumatic bulk material conveying systems and the like.